This invention relates to vehicle fuel systems including a fuel tank and a fill cup for receiving liquid fuel. More particularly, this invention relates to a fuel vapor recirculation systems for communicating fuel vapor from the fuel tank to the fill cup.
It has been recognized that fuel vapor is generated in the fuel tank during operation of the vehicle, for example, by evaporation or by sloshing of the liquid fuel against the walls of the fuel tank. Excessive pressure can build up in the fuel tank as a result of the newly formed fuel vapor unless control devices are provided to vent the fuel vapor from the fuel tank. These control devices communicate the fuel vapor to a canister which contains adsorption agents that are intended to adsorb the fuel vapors.
It has also been recognized that air is drawn into and through the fill cup during refueling. During refueling, flow of fuel into the fill cup and operation of the refueling nozzle creates negative pressure in the fill cup. This negative pressure then draws outside air into the fill cup. This outside air adds to the pressure within the fuel system and must be vented from the system in a manner similar to the fuel vapor mentioned above. However, unlike the fuel vapor, the outside air is not adsorbed by the adsorption agent and is more difficult to pass through the canister. Because of the difficulty in passing air through the canister, a larger canister must be used with the fuel system. This can be somewhat offset if the outside air being drawn into the fill cup is replaced by recirculated fuel vapors.
According to the present invention, a fuel system is provided including a fuel tank, a fuel vapor discharge apparatus coupled to the fuel tank, a fuel delivery apparatus coupled to the fuel tank, and a fuel vapor recirculation apparatus. The fuel tank is formed to include an interior region and the fuel vapor discharge apparatus vents fuel vapor from the interior region of the fuel tank. The fuel delivery apparatus is formed to include an interior region and delivers fuel to the interior region of the fuel tank. The fuel vapor recirculation apparatus is in fluid communication with the interior region of the fuel tank to deliver fuel vapor from the interior region of the fuel tank to the interior region of the fuel delivery apparatus.
The fuel vapor recirculation apparatus includes a sensor, a housing, and a flow restrictor. The sensor is in fluid communication with the interior region of the fuel delivery apparatus to sense pressure extant in the interior region of the fuel delivery apparatus. The flow restrictor is coupled to the sensor and is positioned to lie in the housing to move between a first position restricting the flow of fuel vapor from the fuel tank to the fuel delivery apparatus in response to sensations from the sensor and a second position permitting flow of fuel vapor from the fuel tank to the fuel delivery apparatus in response to sensations from the sensor.
A method for communicating fuel vapor from an interior region of a vehicle fuel tank to an interior region of a fuel delivery apparatus coupled to the vehicle fuel tank is provided. The method includes the steps of providing a conduit and a valve, sensing pressure, and moving the valve. The conduit defines a passage configured to communicate fuel vapor from an interior region of a fuel tank to an interior region of a fuel delivery apparatus. The valve is coupled to the conduit and includes a flow restrictor configured to move between a first position restricting the flow of fuel vapor through the passage and a second position permitting the flow of fuel vapor through the passage and a sensor coupled to the valve. The sensing step senses pressure extant in the interior region of the fuel delivery apparatus. The moving step moves the valve to the second position when pressure extant in the interior region of the fuel delivery apparatus is at a predetermined level.
Additional features of the invention will become apparent to those of ordinary skill in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.